Relax constraint on diff-lcs

The version 1.3 is buggy, the only issue for chef-cli is that now the
diff command will return valid diff outputs :)

See chef#259

chef-cli.gemspec

@@ -47,7 +47,7 @@ Gem::Specification.new do |gem|
   gem.add_dependency "solve", "< 5.0", "> 2.0"
   gem.add_dependency "addressable", ">= 2.3.5", "< 2.9"
   gem.add_dependency "cookbook-omnifetch", "~> 0.5"
-  gem.add_dependency "diff-lcs", ">= 1.0", "< 1.4" # 1.4 changes the output
+  gem.add_dependency "diff-lcs", ">= 1.5"
   gem.add_dependency "pastel", "~> 0.7" # used for policyfile differ
   gem.add_dependency "license-acceptance", ">= 1.0.11", "< 3"
 end